A material that changes color depending upon the light can be represented by a photochromic material. The photochromic material reversibly varies the structure depending upon the incidence of ultraviolet rays and has a property of exhibiting varying absorption spectrum. This is the property of a material in that if an isomer is irradiated with light of a particular wavelength, the single chemical material reversibly forms another isomer having a different absorption spectrum due to the action of light. The formed another isomer resumes the color of the initial isomer due to heat or light of another wavelength.
There have been proposed photochromic spectacles using lenses that have properties of the photochromic material. Outside of a house, the photochromic spectacles quickly develop a color being irradiated with light containing ultraviolet rays such as of sunlight and works as sunglasses. Inside of the house where no light is incident, the photochromic spectacles have its color faded and works as ordinary transparent spectacles.
Lenses having photochromic properties have heretofore been produced by an automated method according to which a lens is, first, arranged by hand at a predetermined position, and the height of the lens and the radius of curvature of the lens, etc. are measured by using sensors. Before being coated with a photochromic coating solution, a primer coating is formed on the surface of the lens as a pre-treatment for the photochromic coating (hereinafter often called photochro-coating) operation in order to improve closely adhering property between the photochromic coating and the lens material. Through a series of operations such as photochro-coating and UV irradiation, a photochro-coated lens is produced by using the coating apparatus.
Therefore, the lens is handed over in a series of processings for coating the lens. In the primer-coating processing and the photochro-coating processing, the lens is subjected to the coating processings while being held by a spin shaft and being rotated about the center axis. Here, it is important that the lens is handed over without deviating the position of the center axis of the lens.
As means for easily handing the lens over to the above spin shaft, we have proposed an apparatus for carrying lenses having a U-shaped lens-holding portion (International Application PCT/JP2006/321923).
FIG. 25 shows a lens-holding portion of a U-shape developed by the present applicant as a related technology (which is not a prior art) of the invention. FIG. 25A is a plan view illustrating a state where a lens 102 supported by a spin shaft 101 is to be supported by a lens-support hand 103 provided in a unit for carrying the lens 102. In order for the lens-holding portion to stably support the lens, it is desired that an adsorbing hole 101a communicated with air adsorption means that is not shown is formed in the central portion of the spin shaft 101 to thereby support the central bottom surface portion of the lens 102 by the suction of the air. It is desired that the lens support hand 103 is provided with a U-shaped lens-support portion 103a, and that an adsorption hole 103b communicated with the air adsorption means that is not shown is formed in the lens-support portion 103a. 
At the time of handing the lens 102 over, the lens-support hand 103 advances toward the spin shaft 101, and, as shown in FIG. 25B, the lens-support portion 103a is arranged just under the lens 102 bestriding the spin shaft 101. Then, the lens support hand 103 is elevated to disengage the lens 102 from the spin shaft 101. The lens-support portion 103a now supports the lens 102. Thereafter, as shown in FIG. 25C, the lens-support hand 103 is moved back. The lens is supported being adsorbed by the adsorbing hole 103b provided in the lens-support portion 103a. While the lens 102 is being carryed, therefore, it does not happen that the lens 102 is deviated or the lens 102 falls. Thus, the lens-support hand 103 carrys the lens to the next step.
To produce a lens (photochromic lens) having photochromic properties, a method (coating method) has been proposed for forming a layer (photochromic coating) having photochromic properties on the surfaces of a lens by using a coating solution containing a photochromic material. As apparatuses therefor, there have been known an apparatus capable of continuously coating a plurality of lenses (see patent document 1) and an apparatus having an auxiliary function for spreading the coating solution (see patent document 2). There has, further, been proposed a photochromic coating apparatus provided with a device for measuring lenses and is capable of forming a photochromic coating maintaining stability (see patent document 3).
Patent document 1: JP-A-2000-334369
Patent document 2: JP-A-2005-13873
Patent document 3: JP-A-2007-127841